arm64: kexec_file: add kernel signature verification support

With this patch, kernel verification can be done without IMA security
subsystem enabled. Turn on CONFIG_KEXEC_VERIFY_SIG instead.

On x86, a signature is embedded into a PE file (Microsoft's format) header
of binary. Since arm64's "Image" can also be seen as a PE file as far as
CONFIG_EFI is enabled, we adopt this format for kernel signing.

You can create a signed kernel image with:
    $ sbsign --key ${KEY} --cert ${CERT} Image

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Reviewed-by: James Morse <james.morse@arm.com>
[will: removed useless pr_debug()]
Signed-off-by: Will Deacon <will.deacon@arm.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 93dc4d36d6db..11f3e1a00588 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -867,6 +867,30 @@ config KEXEC_FILE
 	  for kernel and initramfs as opposed to list of segments as
 	  accepted by previous system call.
 
+config KEXEC_VERIFY_SIG
+	bool "Verify kernel signature during kexec_file_load() syscall"
+	depends on KEXEC_FILE
+	help
+	  Select this option to verify a signature with loaded kernel
+	  image. If configured, any attempt of loading a image without
+	  valid signature will fail.
+
+	  In addition to that option, you need to enable signature
+	  verification for the corresponding kernel image type being
+	  loaded in order for this to work.
+
+config KEXEC_IMAGE_VERIFY_SIG
+	bool "Enable Image signature verification support"
+	default y
+	depends on KEXEC_VERIFY_SIG
+	depends on EFI && SIGNED_PE_FILE_VERIFICATION
+	help
+	  Enable Image signature verification support.
+
+comment "Support for PE file signature verification disabled"
+	depends on KEXEC_VERIFY_SIG
+	depends on !EFI || !SIGNED_PE_FILE_VERIFICATION
+
 config CRASH_DUMP
 	bool "Build kdump crash kernel"
 	help